1. Field of the Invention
The present disclosure relates generally to an image forming apparatus, and, more particularly, to a charging roller used in an image forming apparatus.
2. Description of the Related Art
An image forming apparatus such as, for example, a printer, a facsimile machine, a copier, and a multifunction peripheral, may employ an electro-photographic method of forming an image on a printing medium, e.g., on a sheet of paper. Such an electrophotographic image forming generally involves a charging process, a laser scanning process, a developing process, a transferring process and a fusing process in order to form the image. During the charging process, a charging roller is used to charge a photoconductor to a predetermined electrical potential. During the laser scanning process, a laser scanning unit irradiates light on the charged surface of the photoconductor to thereby form an electrostatic latent image on the photoconductor that corresponds to the desired image. In the developing process, a developing unit supplies developer such as, for example, toner, to the photoconductor so as to develop the electrostatic latent image to thereby form a developer image. In the transferring process, a transferring unit transfers the developer image formed on the photoconductor onto a printing medium. In the fusing process, a fusing unit fuses or melts the developer image onto the printing medium. The electrophotographic image forming is completed with the discharging of the printing medium bearing the fused developer image outside the image forming apparatus.
As the charging roller used in the charging process is driven in contact with the photoconductor, the surface of the charging roller may be subjected to a mechanical shock. In addition, the surface of the charging roller may be subjected to the friction from the toner, additives to toner and/or the developer. Over time, scratches may be formed on the surface of the charging roller, resulting in the inability of the charging roller to uniformly charge the photoconductor to the detriment of the quality of the resulting image.
As the extent of the physical shock that may be imparted on the surface of the charging roller may become greater with the increase in the printing speed, the likelihood of the formation of the scratches is generally higher in the case of high speed image forming apparatuses.